Optical systems are becoming more prevalent in modern communications systems as the demand for high-speed and high-efficiency communications increases. Many optical systems employ waveguides to direct optical signals to optical processing devices. An example of a waveguide includes a slot-line waveguide that operates to guide strongly confined light in a subwavelength-scale low refractive index region surrounded by high refractive index materials to guide the optical signal. Optical systems can be controlled based on optical switching, which can be required to occur at very fast rates and in very small form-factors based on increasing consumer demands.